**Fructose Intolerance**

**Core Concept**
Fructose intolerance refers to the inability to properly digest and metabolize fructose, a simple sugar found in many fruits, honey, and some vegetables. This condition is primarily due to a deficiency in the enzyme fructokinase, which is responsible for phosphorylating fructose to form fructose-1-phosphate.

**Why the Correct Answer is Right**
Fructose intolerance occurs when fructose is not adequately converted into fructose-1-phosphate, leading to its accumulation in the liver. The enzyme fructokinase is involved in this process, and a deficiency in this enzyme results in the inability to properly metabolize fructose. This condition can lead to symptoms such as nausea, vomiting, and abdominal pain after consuming fructose-containing foods.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because fructokinase is the primary enzyme involved in fructose metabolism, not aldolase B.
* **Option B:** This option is incorrect because hereditary fructose intolerance is caused by a deficiency in aldolase B, not fructokinase.
* **Option C:** This option is incorrect because lactose intolerance is due to a deficiency in lactase, an enzyme that breaks down lactose (a disaccharide composed of glucose and galactose), not fructose.

**Clinical Pearl / High-Yield Fact**
A key fact to remember is that fructokinase deficiency is associated with hereditary fructose intolerance, a rare genetic disorder that can lead to severe symptoms if left untreated.

**Correct Answer:** B. Hereditary fructose intolerance is caused by a deficiency in aldolase B.